This invention relates to electric melt and electric boost furnaces and, more particularly, to a method of and apparatus for preventing damage to such furnaces caused by insulation failure or inadvertent grounding of the furnace.
In electric melt and electric boost furnaces for melting electrically conductive material, such as glass for the making of glass fibers, the furnace, as well as steel structures in contact therewith and steel structures proximate thereto, is electrically isolated from ground. The other steel support structures are insulated from both the furnace and the aforesaid structures and are connected electrically to ground by a ground wire, welding or similar means. Generally, building steel, furnace steel, equipment grounds and substation grounds are electrically tied together. In addition, a grounding electrode, i.e., an electrode that is connected to ground potential, is installed in the forehearth of the furnace to protect personnel and equipment in that area.
Prior art electric furnaces have not provided a means for determining that a second ground, i.e., a ground in addition to the grounding electrode, has been imposed on the furnace, for example, by breakdown of the insulation on an electrode jack head assembly. The existence of such a ground, if not detected and cleared, can result in catastrophic refractory failure.
Therefore, it is an object of this invention to provide a method of and apparatus for detecting a ground on an electric melt or electric boost furnace.